Only the proteins that the bacteria escherichia coli (e. coli) needs are synthesized at any given time. for example, when lactose is available in the environment, e. coli will express the lac genes that allow it to break down lactose to obtain energy. when lactose is not present, these genes are not expressed. mc012-1.jpg which prevents the lac genes in the dna of e. coli from being expressed most of the time?

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%

i believe the correct answer is the virus gets an envelope that contains host molecules when it leaves the host cell.

explanation:

during the bidding/release stage of a virus, it encapsulates itself with part of the membrane of the host cells in this case the cells of the monkey and is the reason as to why the scientist found the genetic material of the monkey on the viral cell surface.

further explanation

to understand this answer, we have to know the cycle a virus undergoes to replicate. a virus is basically a bunch of genetic material enclosed in a capsule and lacks any machinery or organelles to ensure their survival so they must enter a host cell in order to get the environment needed to survive. some viruses enter and lyse(destroy) the host cell after they have replicated and undergo the lytic cycle while some enter and leave the cell intact after replicating and these undergo a lysogenic cycle. to enter the cell, they undergo the first process called attachment by binding to specific receptors and co-receptors on the surface of the host cell. after attaching to the cell, they start the second phase called penetration where virus enters or is engulfed whole by the host cell through a process called endocytosis. it is the same process that a cell takes up materials it needs or pathogens around it. uncoating of the virus then happens after the virus has been engulfed and is the third stage. the virus then undergoes releasing of its genetic material in the host's matrix.   the materials then enter the nucleus and undergo biosynthesis by adding themselves in strands of rna being translated and then copies of the virus are produced in addition to the host genetic material. the material/newly formed viral material then undergoes assembly inside the host cell and form a capsule around them. the virus undergoes the last release/budding stage by binding to the host membrane and pushing outwards. in doing so when they tear away from the host membrane, they pick up the genetic material from the membrane of the host cell to form their envelope.

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level: high school

1. the geologists have established a set of principals that can can be used o determine the relative ages of rock. this principal is applied to sedimentary and volcanic rocks. the rocks exposed to wall of grand canyon has layers and by studying the number of horizontal layers in the rock(strata) the relative age can be determined. the layer first formed will appear at the bottom and the the layer of strata last formed appear at the top. by using this information the approximate age of rocks can be determined.

2. carbon dating is used to find the relative age of rock in numbers which means for the rocks that has age between 1-70,000 years.

3. for the rocks of age range between 1,000 - billion of years potassium-argon dating is used.